#!/usr/bin/ruby

require 'socket'


def do_cmd(*cmd)
  ctl = UNIXSocket.open('/run/initctl')
  ctl.puts(cmd.join(' '))
  puts(ctl.readline.chomp)
  exit
end


# These are hashes

$daemons = {}
$daemonCmds = {}

# Needed to prevent respawning during a reboot...

$shuttingDown = false

# Here we do some process monitoring...

Signal.trap(:SIGCHLD) do
  loop do
    begin
      pid = Process.wait(-1, Process::WNOHANG)
      key = $daemons.key(pid)

      if key
        cmd = $daemonCmds[key]
        $daemons.delete(key)
        $daemonCmds.delete(key)

        # Respawn any processes that exit...
        if key != 'openrc' && !$shuttingDown
          launch(key, cmd)
        end
      end

      break if pid == nil
    rescue Errno::ECHILD
      break
    end
  end
end


def launch(id, cmd)
  puts('Starting %s...' % id)
  pid = fork do
    Process.setsid()
    exec(*cmd)
  end
  $daemons[id] = pid
  $daemonCmds[id] = cmd
end


def init
  puts('*** init-ng v1.0.0 starting...')

  launch('openrc', %w[/sbin/rc sysinit])
  Process.wait($daemons['openrc'])

  launch('openrc', %w[/sbin/rc boot])
  Process.wait($daemons['openrc'])

  launch('openrc', %w[/sbin/rc default])
  Process.wait($daemons['openrc'])

end


def shutdown

  $shuttingDown = true
  launch('openrc', %w[/sbin/rc reboot])
  Process.wait($daemons['openrc'])

  sys_sync()

end


# This shows the one of the hazards of coding this in Ruby...

def sys_reboot(cmd)
  # LINUX_REBOOT_CMD_POWER_OFF == 0x4321FEDC
  # LINUX_REBOOT_CMD_RESTART   == 0x01234567
  # LINUX_REBOOT_CMD_HALT      == 0xCDEF0123
  map = { poweroff: 0x4321fedc, restart: 0x01234567, halt: 0xcdef0123 }
  # 169 == SYS_reboot
  # LINUX_REBOOT_MAGIC1  == 0xfee1dead
  # LINUX_REBOOT_MAGIC2C == 0x20112000
  syscall(169, 0xfee1dead, 0x20112000, map[cmd])
end


def sys_sync
  # 162 == SYS_sync
  syscall(162)
end


#
# Start of the script proper
#
# If we're not PID 1, parse & send commands to /run/initctl
#
if $$ != 1
  case ARGV[0]
  when 'poweroff', 'restart', 'halt'
    do_cmd(ARGV[0].to_sym)
  when 'status'
    do_cmd(ARGV.shift.to_sym, *ARGV)
  when 'test'
    map = { poweroff: 0x4321fedc, restart: 0x01234567, halt: 0xcdef0123 }
    # 169 == SYS_reboot
    syscall(169, 0xfee1dead, 0x20112000, map[:poweroff])
  else
    puts('I know the following commands: poweroff, restart, halt, status, test')
    exit 1
  end
end

init

ARGV.each do |e|
  case e
  when 'emergency'
    $emergency = true
  end
end

if $emergency
  launch('agetty1', %w[/sbin/agetty tty1 --noclear --autologin root])
else
  # Launch TTYs...
  (1..5).each do |n|
    launch("agetty#{n}", %W[/sbin/agetty tty#{n} --noclear])
  end
end

begin
  server = UNIXServer.open('/run/initctl')
rescue Errno::EADDRINUSE
  File.delete('/run/initctl')
  retry
end

loop do
  ctl = server.accept
  args = ctl.readline.chomp.split
  cmd = args.shift.to_sym
  case cmd
  when :poweroff, :restart, :halt
    shutdown
    sys_reboot(cmd)
  when :status
#    ctl.puts($daemons[args.first] ? 'ok' : 'dead')
    # This is NFG. It only shows on the main console, not on the socket, so
    # you get nothing if you're ssh'ed in...
    $daemons.each { |key, value| puts(key + ': ' + (value ? '[OK]' : '[!!]') + ' (' + value.to_s + ')') }
    ctl.puts
  end
end